front brakes get stuck partially engagedhttp://tercel4wd.com

[yedi]

PLEASE HELP! The guy I got this 83 tercel wagon 4x4 from said the breaks have been sticking periodically for years and he's sick of dumping money in to it. Every major brake part has been replaced. So I will be driving around and after a while the breaks will slowly start to engage, so I'm driving around with the breaks stuck about half way on. After a while of that they will release the pressure and be fine . What the heck ! posting.php?mode=post&f=4#

[Petros]

Welcome to the list!

Several things can cause this and I doubt the guy replaced everything or this would not be happening. Most common is you need to replace a caliper, they get corrosion around the piston and when you step on the brakes, they do not retract. Solution is to replace or rebuild the caliper. If you carry a jack with you, and it is hanging up, jack up each front tires (in turn) and see which wheel is difficult to rotate start with front wheels (engine off, trans in neutral).

If you try this test, also have an 8 mm box end wrench handy, and once you found the wheel with the stuck brakes (wheel will not turn easy), turn steering wheel to full lock to make access easier to the caliper and loosen the bleeder valve with the 8 mm wrench one turn and than re-tighten. You will get a squirt of brake fluid out of the bleed valve, and if the wheel can than rotate freely; you need to replace the brake flex line. When they start breaking down internally they will act like one way valves. Sometimes you can see it on the outside (line is lumpy) but I would not count on a visual inspection. IF the wheel is still locked up after you open the bleed valve, than it is the caliper that is frozen. Replace the caliper.

Rarely but occasionally the check valve in the master cylinder will not bleed off the pressure, you will know this if both front wheels lock up at the same time. It means the whole system stays pressurized. Rebuild or replace the master brake cylinder.

It is possible someone put the wrong kind of brake fluid in the system and it is causing all the rubber parts to break down, swell up, and block off the hydraulics, also locking up the system. IF that is the case all the parts with rubber have to be replaced (master cyl, all 3 flex hoses, front calipers and rear cylinders), and you have to flush out all the hydraulic lines very well to clear out the contamination. Than the system is filled with the proper fluid and bled out. when the wrong type of fluid is used it causes the synthetic rubber to break down, and swell up. The previous owner may have caused that.

Either way a proper repair and replacement of the damaged parts will solve the problem. It is a matter of proper diagnosis and repair. Only use DOT 3 brake fluid.

And I would not take it back to where the previous owner had is serviced, they are either incompetent or crooks.

If it is always the same one wheel that locks up, than the problem is isolated to either that caliper or flex hose on that wheel, if not it could be a system wide problem.

Anyone who works on brakes should know how to diagnose and repair this kind of problem, if the previous owner's mechanic does not know how to fix it and I would take it elsewhere. Personal this is why I do my own repairs and topping up of fluids, than I am not subject to incompetence, rip-offs, or a mechanic doing damage to my car because they were ignorant of what it needs.

None of these repairs are that difficult btw, and you should consider doing them yourself. You will learn a lot and save a lot of money.

Good luck.

[dlb]

so much excellent information in that post, petros! useful stuff. i've never heard of the flex lines acting like one way valves.

on the topic of different brake fluid, dot 4 has a higher temperature tolerance because it is intended for vehicles with ABS but it is compatible with dot 3. dot 5 will not mix with either dot 3 or 4 though because it is silicone based while the other two are glycol based. no way to tell what a PO put in though so do the tests that petros recommends.

[yedi]

Thanks yall ! now I have good idea of what to do or at least what to look for to head me in the right direction. I will give an update - peace - Yedi PS. I'll try to post some pictures of my tercel.

[Petros]

i've never heard of the flex lines acting like one way valves.

I would have never believed it either until it happened to me. I had an old beater chevy van I bought for $100, one of the front brakes was locking up on me. IF I let it sit it would bleed off the pressure and I could drive it again. I bought a reman caliper (only $25) and installed it, but the problem did not go away, but got worse. I was about 20 miles from home, I would drive very carefully using only the parking brake to slow down to not pressurize the system. Inevitably some idiot would cut in front of me and I would have to use the brake pedal, and pull over to the curb, jump out and quick open the bleeder valve to relive the pressure on the one wheel, and jump back in and keep going (I had to do it three times before I got home).

I bought a new flex line (only $7) on the way home, installed it and bled it. Problem solved. The guy in the parts stores said that is not unusual with older Detroit cars. A flap of lining inside the hose comes loose and acts like a one way valve. I have owned old Volvos, Mercedes, porches, Datsuns, Nissans, Toyota, etc. etc. and never seen this before until I owned an old Chevy.

I suppose it is possible with any car, but chevy van was "only" as old as my Tercel4wd at the time. More likely it could happen if the flex hose lining was breaking down because the wrong fluid is eating away at the rubber.

[splatterdog]

Hoses usually only go check valve with a contamination. The only ones I've seen that weren't, were on a volvo and cadillac. Otherwise they usually fail from the outside-in till they rupture.

Couple things here. First I would check the booster push rod adjustment. Also I would look at the brake pedal to make sure it's returning fully. If there is a return spring, make sure it isn't broken.

When doing the hose check as petros said, start at the steel line side. Then you will know it isn't upstream. Then crack the bleeder to check the hose for "check valving".

[takza]

Flex hoses have a "nylon" core that can get too hot and melt partially closed....thus the one way effect. 1st the caliper sticks and overheats...then the hose melts...then things get worse.